1. Field of the Disclosure
The present disclosure relates generally to data processing units, and more particularly to data processing systems having multiple processing cores.
2. Description of the Related Art
A data processing system, such as a computer system, typically employs one or more data processing units, such as central processing units (CPU) and graphical processing units (GPU), to execute tasks. Each data processing unit can have one or more processing cores, whereby each processing core is capable of executing tasks independently. Each processing core is composed of millions or billions of solid-state electronic devices, such as transistors. For example, many processing cores are composed of insulated gate field effect transistors (FETs).
The performance of a FET device can degrade over time. A typical cause of performance degradation is bias temperature instability (BTI), which refers to an increase in the absolute value of the FET's threshold voltage and consequent decrease in source/drain current and transconductance of the FET device. This performance degradation of the FETs can cause degradation in performance of the processing core associated with MOS device. BTI can result from a number of factors, such as charge trapping and interface states in the gate oxide of a FET device. In particular, negative bias temperature instability (NBTI) can occur in p-channel FET devices biased with negative gate voltages. Positive bias temperature instability (PBTI) can occur in n-channel MOS devices. Process technologies that make use of high-K dielectric materials can be especially susceptible to bias temperature instability. The increase to threshold voltages of the MOS devices due to BTI can eventually lead to failure of the data processing unit.